Torsion spring suspension for tandem axle vehicles



L. K. LOEHR Feb. 2, 1960 IoRsIoN SPRING SUSPENSION FOR TANDEN AXLE VEHICLES Filed March 27. 1957 i12-- 2 Sheets-Sheet l *ff 'Alun' IIIII/ Feb. 2, 1960 L K, LOEHR 2,923,556

TORSION SPRING SUSPENSION FOR TANDEM AXLE VEHICLES Filed March 27, 1957 2 Sheets-Sheet 2 .lull

lllI

INvENToR niteci States Patent TORSIUN SPRING SUSPENSION FOR TNDEM AXLE. VEHICLES,

Leslie K. Loehr, Los Angeles, Calif. `Application March `27 1957, Serial No, 648,821() '1V claims. (ci. 28o-104.5)

This'invention relates generally to spring suspension systems for load-.carrying 'wheeled vehicles andA particularly to torsion spring suspension systems ofcftliischaraeter employed on vehicles Ihaving wheelsupporting.4 axles arranged in tandem relationship under the'load-carrying structure such that loads carriedA bythe axles. are`r distributed equally to thewheels on the ends of' the;y axles.

It is customary in conventional spring suspensionsystems of the type used on` vehicles. having dual tandem axles, to employ semielliptical leaf!` springs-for connectf ing; the axles to thevehicle load-carrying structure. In 111,68 systems, the ends of the leaf springs'are usually connected tothe vehicle frame by suitable shackles arranged tofpermit movement ofV thef springsv in vertical planes extending lengthwise of the vehicle. Thus, when theends ofv the axles move relative to eachother, such as: fsf example. when 0111er axle. en@ mdves 9p toward Athe vehicle frame and the other end moves A'down away romV-the-- frame, the springs are subjected to severe. twisting forces applied byr the axles to the centers of the springs and, resisted by theshackles at the ends'oi the springs, Although a leaf spring is an excellent device for, absorbing forces applied in certain directions, the ability tov absorb twisting forces of the above-recited nature is not among its faculties, and attempts toattenuate these forces have consisted mainly of insertingrubber bnshingls in the connections 4between the shackles and the ends of the springs, and between the. springs and the axles.

Ontrucks having live tandemr axles,A a typeofv construction` wherein the wheels of b othy axlesare driven, it is GOIDLIOII practice to employ as spring suspension system in which two'walking beams areconnected at their'I ends to vtheaxles (usually with rubberbushings), and the center of each'beam is connected-to. the center of 'a leaf springlby means of a rocking pin having` its axis. arranged in parallel relationship withv respect'to vthefaxles, while icc 2 longitudinal directions relative to the frame; and where walking beams are used, the axles swing on radii' about the axes of the rocking pins, which, in effect, results in similar longitudinal movements o f the axles with respect to the vehicle frame. i

A further disadvantage of the system having leaf springs directly connected to the axles resides in the condition known as spring windup. In otherrwords, when driving torque or braking forces Vare applied to the wheels such forces momentarily feed energies to the springs,` which energies'are quickly returnedto the wheels cans-1 ing. clutch and brake chatter.

. only-,by not feeding win'dup energy into the springs;

. sion system for trucks, trailers, and other vehicles having the "ends of the spring are connected to the frame by suitable shackles. In this case, the twisting forces are absorbed by the beam and the rubber bushings connecting vthe beam'to the axles. However, since walking beams arefemployed as an expedient toward maintaining the axles in `aY generally parallel4 relationship under inost operating conditions, it follows that the rubber bushings will afford the ability to absorb only alimited amount frelativemovement between the. ends of the vbeams and the axle; hence, the allowable transverse tilting movement of the axleswith respect to theY frame and with respect to eachother is also'. limited.

Another disadvantage characteristic offboth ythe above described. suspension systems resides in the fact that the axles are not maintained in parallel vertical planes under all conditions` of yvertical ymovement relative to the vehicle frame. For example, where th'e center ofthe semielliptic springs are connected to the axles, one end ofieach spring is .shackled to the `frame .about axed axis, thus, as the "springs deilectoratten, the axleav swing'on'radii about such xedaxesythereby `causing theMaxles-to move-in dual tandem axles, which is not only constructed so as;

tosconne the movements of the tandem axles to generally vertical planesextending transversely of the vehicle at substantially right angles to the longitudinal axis tliereof under all conditionsof spring deflections, but'it is further constructed so thatloads transmitted by the axles to the Wheels are eiectively equalized for all positions of the axles in the generally vertical planes, and sot-hat energies resulting from brake and driving forces applied to thesek wheels are absorbed by the vehicle frame such as to prevent these energies fromrbeing ted back tosaid wheels. g l L The spring suspension system as above contemplated is made practicable by the use of split-walled tubular springv elements constructed and supported according tothe teachings set forth incopending U.S.V patent application Serial No. 591,989 led June 8, 1956. In this in-` vention, a pair of split-walled tubular spring elementsis; supported along` each side of the vehicle frame in endetof end proximity so that the elements extend lengthwise of:- the vehicle with their axes lying in a common plane above:v

the axles on. one side of the vehicle. The distal ends: of each pair' of spring elements are coupled tofrespective axles by 'suitableshackle means having pivotal axesqextending lengthwise of the vehicle and transversely of the axles, which shackle means apply twisting forces to the spring elements according to thej loads transmitted ltothe axles; while theproximal ends of eachV pair are coupled in lforceftransrnitting relationship by equalizing; meansadapted to effect an equal distribution ofV the loads 4between the tandemly disposed wheels on the respective side of the vehicle. Moreover, the present system further contemplates a type of springsuspension` whereini Vthe load-carrying capacity of the spring employed may be selectivelyaltered,y either manually or automatically, to provide differentdegrees of spring flexibility fordifferently loaded` conditions of the load-carrying portion of the vehicle or, in other words, to provide adjustability to the springiness of the springs so that an empty vehiclek will ride as easily.` asl a vehicle thatV is loaded'. Thisad'- justable `featurefis'als'o made possible bythe Vsplit-walled tubular spring elements, and by the adjustable natureof the equaliziing means.

Accordingly, itis an'object of the present invention to provide a springsusp'ension system for use inlloadicarry ing Wheeled vehicleslhaving dual tandem aXles-i'n'which movements-ofthe Vtandem axlesrelative to' the load-carryl ingstructure are confinedV to generally vertical lplanes e-xv tending transversely of the vehicle, andto. provide asystemin which a pair ofsplit` tubularme'rnbets massa Feedback energy of this character produces a bouncing condition of the wheels and the load-carrying portion of the vehicle, which, whenv caused by the brakes, is responsible for many accidents: due to brake failure on heavy trucks and trailers ,travel-- ing down grade at relatively high speed. This bouncingr condition is cumulative, and' once started it can be stoppedl forces are positively precluded.

' tionof the weightof said suspension system.j"fl The novel features'ofthis invention,A together with the vehicle portion shown in Fig. l;

prise Athe spring elements i side of the loadcarrying structure.

It is another object to provide such a spring suspension connecting'the axles to each t system characterized by ability to equalize weight distribution between-wheelsmounted on the ends of the tani demaxles. 4 v V ""It is a further object to provide Ysuch a spring suspen* sion' SYStem Which'is equally well adapted for Vusewith tandemly disposed axle structures having power driven wheels 'or withtandernly disposed axle structures'having Vwheels thatl Vare not `power driven,- or a combint'ion of both 'such axlefstructures arranged in tandem. h v

It is an additional object o f the invention to providea suspension system of the above characterwhe'reby-pdriv'- ing "forces and/oi" brakingfo'rces applied to` the" wheels mounted ony the ends of the axle structures are transmitted directly to the vehicleY load-carrying vstructure such that i deflections of the spring elements of the system Aby;su :rh

lIt is also-an object oi the presentrinvention toprovide a spring suspension system Vfor connecting dualaxles-.i

Vtandem under theload-carrying'portion ofra load-carry# ing wheeledvehicl'e, which Yis characterizedby adjustabilchanging the spring-borne condition of the load-carrying structure accordingA to the Vloads being carriedltherefby;

and to further provide such arsystem wherein the'tdtal weight of the load-carrying portion includesamajor por `further objects and advantages thereof, will be` better 'understood f rornthe' following descriptionvconsidered in p ity in the springiness of the spring elements 'employed for 25` connection `with the accompanying drawings in'which an structures embodying thisinvention; i

Fig; 2 talken on liner2'-`2 of Fig. 1,V is a'plan yie'wrrep resentati-ve of the-Yst'ructuresgemployed on both'sides of fFigl'4 taken online 4 4 of Fig. l, is a se ctional view i representative of the structures connecting the dual axles f tlFig. 5 V1s; a'sectional view taken on line 54-'5 of Fig, -3;\V Fig. 6 is a sectional-view' takenon line l6'-,6opfFilg.`- 3;

to' both'sidesfof `the vehiclelportion shown in Figi;`

Fig.7,' taken on Aliner 7%-7 of Fig. 1, is a-planiview showing dual wheel-supporting axles connected to side members of thevehicle frame; andf Figi.` 8,' taken on line 8-8 of Fig. 7, shows the struc ture of Fig. 5 `With modifications.

a definition o f the` of thefin Thewheeled vehicle, of which a portion'is shown-inV` It is to be "distal ends of spring ,elements andiitt". spliti walled characteristics ofr spring elements V20,- 20V `are shown in Figs. 3, 4 and 6 where reference numerals 21,

21' indicate gaps orslits infthe walls of the tubular elei ments.

In supporting spring elementsV 20, 20', as above described `and shown in Fig. 1,brackets 25, @5' are provided with portions 25a, 25a' extending downwardly from side member i12,j which'` circumferentially embrace the spring elementsnearV thero'utboard ordistal ends thereof; While a housing 31 of 'equalizer 30,dependent fromV frame member'lZisprovided wtih side portions 31a and 31b which likewise g` circumferentiallyA `embrace v the spring elements at their inbo'ard or. proximal ends, as seen in` Fig, 3. Thus, spring elements 20` and 20 arrevnot only supported by the lvehicle frame, but the character of this support is `such as to allow rotary and/ or axial movement ofthese elements relativento the hanger brackets.andgthel equalizexfhousing, and such as to `provide radial movements'fofthe elements split walls.` `This is* an essential fea; ture of `thefstru'eture employed for supporting split-walled tubular springs because .torsional deflection 'ofsuch springs isiaccompanied by helical warping of the ywallof-thetu` bularfspring, characterized: by relative infn/ement' 4in opposite axial `direction ofitlie tube `walliportionsjfaclng each otherracross'the splitior gapQsuch as gap 21, Fig. A4,"and by a tendencyof such wall portions'to move 'radially particularlyA atthe endsof the spring.`

f VVAccording`to rthw `present embodiment, equalizerfis p seen Vin Figs. 3f and `5f is a mechanism that not only sup# ports elements V20, 20T 'in-end-to-end proximity,` but/itali Y so interconnects'vtheends so held in a force transmitting relationship. `characterized bythe fact that rotary movement'offonefspng element `irrone directionfcauses the .other spring element to rotate an `equal amount `in the `other direction `This condition is effected 'bye-agear train" comprisingtbevelfgears 32, 32 drivinglyconnected A 33; 33'1:threaddlylengaginghubsza, af'ofthe respeci" f Vto the proxirrialends"` ofi'spring' elements, 29' with pins tive gears, fand' reversing Apinions or idler gears 34; 34'- mounted on a` shaftfS'S adjustably supported in Housing 31 byY aring gear 36 in drivenengagement with ajvvrni i '37, as shown in Fig.` 5.

` "I Fig.3 is asectional view takenon lineioffFig; p

i Lever arms- 40`and"40, seen in Figs! 1, `Y2.,"and are rigid structural niembershaving side 'elements 41, 42 'and 41', 42` separated by spreader elements43, 43Vsuch thatV each member `has in general, an H-shaped contiguration Side elements 41,42; 41' and 42 are' respectively provided with end portions 45, 46, 45` and ',46` bored .tofciri eumferentially embrace tubular spring elements 20 and 420',1 and'withgend portions 47, 48, 47 and 48l pivotallyr connected tod'o'wnwardly projecting lugs 51, 52,*51 and sz'rof intr'ssoand` sotby pivot pins sa, 54, ss'f and 54,'

Figs. l and 7,` is so constructed as to includefa longitui i dinal` axis 10, VaA load-carrying frame identiied'byframe Vside memhers'll and 12, and dual wheel-supporting 'axles 14 and 1'5 suspended transversely `of the vehicle axis in Y parallel tandem relationship fromthe vehiclefframe by i two identicalfspring suspension assemblies (one from each side member) such las assembly VA seen'i'n Figs. 1 Yand'ZV where apair of split-walledftubular spring elements 20 Y. and 20' are shown supported inan end-.to-end interconnected relationship (see Fig. 3) with their axes in` a common plane below the vehicle frame by hanger brackets 2525'and an equalizer 30 all connected to frame side member 12 by boltsV 18 suchjthat the spring elements extend in opposite directions lengthwise of thevehicle frame and transversely of j-axlesf'14 and 15, and where .lever arms 40, 40', linksr50, 50?; and axle brackets 60,1 6'10' cooperate to connectaxles; 14and1'5 to the outboard or extending through `openings in ends`47, 48, 47` and `48f i and threadedly vreceived by the lugs,j according `toxFig. `1.

Axles brackets and 560'; also` according to theviewjn Fig. 1, Yare U-shapedmembers `of rigidconstructin piv otally connectedrtoflinkis `50 and 50.by pivot pins 61, 62,.'

61 and `62' extending through openingsin the upperen'ds fof legs 63, i64,153? and 64" of the `axle Vbracketsjirito threaded engagements .'wit'h the links jas indicatedh by dottedlinesff.' v l i' It is Vto be noted that end portions"` 45 Yand 45' ofllever arms 40and 40f not only circumferentially embrace pori 'tions' offsplit-walled tubular; spring elements 20 and20",

but they are drivenly'connected `to saidportions by suit? able shoulder `screws ,70 and 70",such that helical warp- Y ing or twisting of the'spring elements is accommodated and radical'displacement of the embraced portions ofthe splitwalls is precluded. Assihown,` screws 701and 70'1 extend through `radial openings inend-portions 45, A45' and'` through radialopenings in the distal ends of .the

w spring elements intoj threaded openings `in alignment` inembers'jland 71'., of whichthe latter operate ,tdtnainl` fo be further noted'thatlaxflel brcketsviand "60' Yfa constructed to includemounting pads 66 and 66f which coacl: with U`b`olts" 67 inf rigidly'eon1iec't'ingiy these Brackets tofaxles 'I4 and 15 such that yaxes of theo'p y rigs n he upper ends'of legs 63, 64, `63"and Vv64 refdisposedat right angles tothe axes of the axles. Thus,'lever 40 and 40', links '50 and '50', and laxlebracketsf't L*and 60 cooperate with the pivot 'pins' to form-shacklelinkages or articulated couplings connecting the Vdistaleidsfof 'spring elements "20' and 2W to axles1i4 nd l15 ls'ueh that up and clown movementsV lof the `tuiles relative tothe vehicle frame produces forces twistiigly vapplied -toth'e distal ends of the spring'elerneiitfs. y

An important feature of1the'prsent-invention 'resides in the fact that the'up and `dbwn-fiiiovemefri'ts of axles 14 and relative to the vehicle load-carrying frame are confined to vertical planes'extending trans y of lthe frame at right angles tothe longitudinal'axis ofthe' vehicle. This feature results from" the par'all'e'lrel'ationships of the Afunctional ax'esof 4suspension assembly with respect to each other and with' res'pe tito axis the vehicle, and from the right angle relationship "of these'functional axes' with respect l'to'.'the VaxesV of the axles. In other Words, fthe laxesy off-'springlelements-20 and 20, and the axes of the pivot lpins cotinecti nls 50,-50' between lever armsdt), 40"'and axle b'r'ackJ s60, 60 are not only parallel with respect to efa'ch other andi the longitudinal axis 10 of the'lo'ad-'carrying frame; but

they are disposed at right angles witlifres'pectf'to the longitudinal axis 10 `for all v'possible `conditions wherein` the weight of the vehicle frame aridllb'ads' carriedtlieieb'y are.k transmitted through tl"i't`e axlesY to wheels 80? and 81' (schematically representedL byr dotted lines) 'supportedA by the axle'sac'cordingto any of the wellknownpracticesv For instance', thecros's section'alview of` 0f theprio'r art. Fig- 44` is representative of-th'eV twosuspension assemblies Afi'nterconnecting axle-14 to framel-sidememb'ers 11 and-- .12;- InV this View, let it'be assumed thatrbothie'nds of the axle move equal distancesv in the `s'arne'direction relativev to the'frame, in which case ,line 82 indicates` the path of movement of axle bracket 50.' Then, let it bel assumed that'onlyvone end of the axle movesV relative to the'framd inwhich case line Sindicates `an arcuate patli'of move' ment of bracket 60;Y Howevenin both cases pivot pins 53 and 54 swing in an are 34 describedby lever` arm 40` about'the central axis of' spring'elenent' '20,1y for which compensation to prevent later'aldisplac'ementof the axle-` with respect to the vehicle 4frameis provided by'v -a-lateral swinging movement oflink 50about pivot .pins lfrand 62 in an arcuate path 85. In other words swinging'A move-` ment of lever arm- `about the axis of Vspring element f2.0I is accompanied by"a swinging-movement Vof link'50about the axis of pivot pins 61 and 62; Y

Having described the Structural-connections between the vehicle frame and axles-14 and 15 the advantageous effects of equalizer 30jwill now be described;` To fully understand the importance of these eiects, it must be remembered that tubular Yelements 20. and 20 are'not only torsionally detlectable, butvthey are constructed yof spring material, such as spring steel; hence, they are'also torsionally resilient.

Let it be assumed for purposes of description,- that the vehicle load-carrying structure represented by fraine side members 11 and 12, and axle'15 are fixed or immovable move inV its respective vertical planet t of spring'elementrZG toward the distal vend ofspring ele' in equalizer housing 31-bya ringgear` 36 in driven`en gagement with a worm 37; Vhence', pin 35 ,ifsstationary,l and', v

nient 20' along the aligned axes of these elements, tlie rotational movement of lever arni'40 is in a :ou'nter-l clockwise direction; hence, bevel gear 32 of equalizer 30 is' caused to rotate counterclockwise, which rotation is reversedy by idler gears 34 and'3`4' `such that bevel gear 32 i's caused to rotate clockwise and drive spring element 20 in a clockwise direction. However, since the vehicle frame and axle 15 are immovable withresprect lto each other, the force system including hanger brackets 25 and equalizer housing 31 is 'so constituted that clockwise rotatijoniof the distal lend of spring'element 20 is effectively prevented by aV counterclockwi'se force applied .to 4the t spring element 21' distalV end byarm 40 through end porti'n'r`45 of the lever arm sideelement 41 and shoulder screw'r70.V Y Y In view of the fact that the distal end of spring element 20 is4 prevented from rotating in response to the rotation of the distal end of spring element 20, it follows that one'or both `of the spring elements, accommodate this situation by deflecting` torsionall'yl Thus, by constructing spring elements 2.0 and 20 sofas to provide theA same deflection qualities for the same twisting forces, both elements will deflect equal amounts and in opposite directions in the labove` describedsituation, because of equalizer 30 which not only operates to reverse thev sense of thetwisting forces applied tothe proximal ends of spring elements 20 and 20', but it alsol operatesto divide vsuch twisting forces equally between both spring( elements regardless of the positions of axles 14 and `15in their respective vertical planes of movement relative to Y connected to the proximal ends o f the 7springelements attempt to rotate inthe4 ysame counterclockwis direction but areprevented from such rotation by idlerrgeai's and 34. In this connection it mustl be remembered that pin 35, rotatively supporting the'idler gears, isisuppo'rtfed any inequality in the forces applied to idler gears 34y a` 3 4f by gears 32l and 32' causesfthe idlerv gears to rotate! on pin' 35' until the forces applied'by gears 32, 32 afr equalized. i t .l

The adjustable feature provided pin 35,` with respect."l toits relative radial position in housing 3\1, is` an impor-v tant characteristic of this invention because it permits the proximal ends of spring elements 20 and 20 to be rotatedwith respect to the equalizer housing for increasing or'4 decreasing the torsional stiffness of yspring elements20f; and 20' to accommodate,differentlyloaded conditions of; the1vehicleload-carrying frame. In conventional leaf.

' spring suspension systems, adjustments of the springgstifY nessis highly impracticable; thus, in a vehicle having a. load-carrying frame weighing 2000 pounds and a leaf such a vehicle were equipped with the, present invention,, the equalizerrcould be easily adjusted to provide eifectivc; sprnginess under bothempty and fully loaded-conditions 1,

of the load-carrying frame.-y

' ment` withrotating structures mounted o n the wheels:`

accesso precluded. Y

.Anothergadvantage of the `spring suspension system brake' andiclutch de, atter causedby feedback energy is herein disclosed, resides in the fact that `much l,of `the endshaft 39 .of worm 37 extending outwardly of case 31. 5

Another means of changing the statically deflected conditions of spring elements 20 and 20' comprisesa power driven mechanism 90 schematically indicated in Fig.Y 8,

which `is drivingly connected to worm 37 through` an extension 9170i wormdrive shaft 39. maybe selectively controlled by manually operable devices or it may be automatically controlled by devices responsive to prolonged changes inthe relative positions of` the axles with respectto the loadcarrying frame. In either case, where 'mechanism would be omitted. Although it is' an object of the present inventionito provide spring suspension systems equally well adapted structural details for connecting such wheelsto the Vlaides,v as well as thebrakernechanisms, have'been omitted, be-

cause structures of thiskzharact'erarev wellknown in the art; therefore, it Yis tofbe understood that axles 14 and 15,

Mechanism 90 10 weight of this system is added to the weight of the loadcarrying structure; `therefore it becomes sprung weight,`

or weight that actually effecting torsional deflection of the split-walled tubular springs. n `What isclaimed as newis: Y l 1.'In a vehiclel having aV load-carryingframe and a pair of transversely-,extending `tandemly-disposed .axles withvload-supporting :wheels `journaled on the` ends of said axles, a pair of springtzassemblie's,interconnecting Y the vehicle frameand the Vaxles such that saidfrarne is 9o is employed, mites 15 Vtendencies fof-lthe `slot-forming wall `portions` to lmove i radiallyat the ends` of `said spring members `when twist-` and Awheels 80 and 81 are representative' of ,driving axles 25 and wheels,'nondriving axles'and wheels,and a eombination of driving'and non-driving axles and wheels and it s to be further understood thatall suchY axles and'wheels may be equipped' with suitable braking mechanisms-,accordingto requirements. f

tionY to: theV torsional loadings, tubularV spring' elements Q0 and 20 yare subjected 4to transverse loadings resultingv `from `the force systemwhereby the weight of the' lad- `Examining Figs. 1 and' `4, it will be seen that, inaddicarryingY structu'reis'transmitted to the axles." `Stated A35 diierently, equalizerfhousing side portions Sla'and 3112,;

andfhanger' brackets 25 and 25 transmit ,thel weight of .the"vehicle"fr`ame tospring elements 20 and 20"` such that the'forces resulting from the weight are at right angles tothe spring element axes.` Now,"theseweight 40 forces larefresisted by counteracting "forces originated.. by thewheels and applied to spring elements 20`a1`1d 20'T byend portions 4 5, 46, 45.' and 46v of -le'ver` arms 40'and` v 40 at different axiallocations along. the spring elements spaced from housing side portions 31a; 3112 fandbrackets 25, 25'; hence, the spring elements act vasimembers `subjected to bending loads` inaddition to torsionalloads; of i Y Which'thje latter result from actions of lever .arms 40 and s Y 4 0' in transferring y,theweight of -the vehic1eload-carryin`g strncthreto.` axles `14 'and 15` through 5i), 501 5 Inbrake vmechanisms employed on wheeled vehiclesnnon-rotating structures are rigidly mounted on the wheelsupportingV axles, 'and are `adapted ,for frictional engagethus, when the brakes areactuate'd, frictional forces between theA `rotating and non-rotatingV structuresproduce important .feature resulting from vthe fact that thefdirection of spring elementfdeections is inl eifect, at right angles to the `direction ofthe twisting forcesapplied to the axles. VMoreover, this ability to transmit brake-reresiliently. supported on said axles, each of said pair of spring assemblies comprising: a pair of tube-like: torsion spring members having longitdiualrvaxes andwgenerally Ycylindricalwalls withraxially disposed slots extending Ythe 'for' use 1n veh1cles having driving and/or Vnon-driving wheels equipped with suitableY braking mechanisms, the 2()v full `lengths of y,said wallsV whereby said walls areV pro vided with helicoidal` ,warping abilities characterized `by ing forces are Ktwis'tinglyapplied to said members; first means coupling `the pair` ofA spring ,members in force` transmitting axially-,aligned end-to-end relationship `such thattwisting onefof the pair of members about its axis in, eitl'1er` direction yeffects; twisting of` the,` other member inthe opposite direction, said `iirst means circumferen-` tiallyembracingthe.cylindrical walls of the proximate ends.k of theV pair of spring members such that the helicoidal warping abilities of said cylindrical walls` are a c :ommodated,fand` such that radial movements from the radial-movement'tendenciesvof the slot-forming wall portions `are precluded; load-transmitting linkages ,conf nectingrthe tube-like spring members to-respective., portions ofthe transversely-extending tandem axles, said VYlinkages including elementstcircumferentially embracing Lthe cylindricalnwalls ofthe distal endsof said spring members and; spring-membertwisting connections between. said elements l and `said embraced-Wall portions,

` said embracements and spring-twisting connections being 'of azcharacter to accommodate the helicoidal warping'abilities of said cylindrical` walls and preclude movement from the radial-movement tendencies of the slot-` lof forming wall portions atthe distal endsiof thespring members;,and second means connecting the pair of tubelike spring members to one` side. of the *load-carrying frame in transvere relationship with respect to the tandem` axles, saidsecond means being constructed and arranged to, cooperate with the first means and the-dipad-trans` mitting linkages such that weight of the.vehicle'irame Qcal walls. with axially disposed .slots extending the r'ullV lengths ofsaid walls `for providing said'sprmg membersz action forces .directlyto the frame is also effectivjefto transmit driving reaction torque directly to the frame; thus, when a vehicle having driving wheels changes from Va standstill condition toene of wheel-driven motion,

counter driving torque is transmitted'directly tothe load- Y carrying-frame withoutcansing spring 'deections Since spring; deflections flare prevented under the conditions abovedescribedg'ener'gy isnot stored in the springs, constransmitted .to said axles as forces vtwistingly applied to said spring members;

l2. In .a vehicle-having a 10aa-carrying nieanaa pair of transversely-extending tandemlydxsposed axles with ,load-supporting Ywheels journaled onthe ends of`` saidffaxles, a pair `of spring assemblies .interconnecting the` vehicle frame and thexaxles` such that said. fr ame 1s` resiliently supported on said axles, each .of sa1d `spring assemblies comprising:y a pair of tube-like torsion `sprlngl members having longitudinal axes and generally cylindrif with abilities totwist throughout their'lengths in response to forcestwistingly applied thereto, said twisting abilities being characterized by relative movements lne-.- tween the slot-forming wall portions `when said `spring members 'are' twisted; lirst 'means coupling the tnbe-like spring members in force-transrnitt1ng axially-aligned end- 0. toend relationship such that twisting one member in eithervdirectioneiects an oppositely twisted eondltiomof` the` other member, andsuch that characterizing `twisting abilities fsa'id spring members are accommodated; loadtransmitting i. linkages connecting the `tube-like spring i members to. respective portions of,` the transversely ex-i tending tandem axles, said linkages including elements circumferentially embracing portions of the cylindrical walls of said spring members, and spring-member-twisting connections between said elements and said embracedwall portions, said embracements and spring-twisting connections being such that the characterizing twisting abilities of said spring members lare accommodated; and second means connecting the tube-like spring ymembers to one side of the load-carrying frame in crosswise relationship with respect to the tandem axles, said second means being so constructed and arranged that weight of said load-carrying frame is transversely carried by said spring members and is transmitted to said axles as forces twistingly applied to said spring members through cooperative action of the rst means and the load-transmitting linkages.

3. In a vehicle having a load-carrying frame and a pair of tandemly disposed axles with load-supporting wheels journaled on the ends of said axles, a pair of spring assemblies interconnecting the vehicle frame and the axles such that said frame is resiliently supported on said axles, each of said spring assemblies comprising: a torsion spring including a pair of tube-like members having longitudinal axes and generally cylindrical Walls with axially disposed slots extending the full lengths of said walls for providing said tube-like members with abilities to twist throughout their lengths in response to forces twistingly applied thereto, said twisting abilities being characterized by relative movements between the slot-forming wall portions when said tube-like members are twisted, and including a force-reversing mechanism coupling the pair of tube-like members in force-transmitting axially-aligned end-to-end relationship so as to accommodate the twisting abilities of said members, and such that a force twistingly applied to one tube-like member in one direction is twistingly applied to the other tube-like member in an opposite direction; load-transmitting linkages connecting the torsion spring to respective portions of tandemly disposed axles, said linkages including elements circumferentially embracing portions of the cylindrical walls of the pair of tube-like members,

and member-twisting connectionsbetween said elements and said embraced-wall portions, said embracements and said member-twisting connections being such as to accommodate the characterizing twisting abilities of said tube-like members; and support means connecting the torsion spring to one side of the load-carrying frame in crosswise relationship to the tandemly disposed axles, said support means including brackets circumferentially embracing portions of the cylindrical walls of the torsion spring tube-like members such that said one side of the load-carrying frame is supported by said tube-like members from said axles through the load-transmitting linkages, and such that forces resulting from this supporting action are directly applied to said members cylindrical walls transversely of the members axes and converted to torsion-spring-twisting forces twistingly applied to the pair of tube-like members by the load-transmitting linkages and the force-reversing mechanism of the torsion spring.

4. The combination dened in claim 3 in which one of said linkages is characterized by a pair of spacedapart elements withv end portions rotatably receiving the cylindrical wall of a tube-like member, and by the fact that one of said end portions is drivingly connected to said wall so as to constitute a member-twisting connection for said one linkage.

5. The combination defined in claim 3 wherein the force-reversing mechanism is mounted on said one side of the load-carrying frame such as to cooperate with said brackets to constitute the support means.

6` The combination defined in claim 5 wherein the force-reversing mechanism included means drivingly coupled Ato the proximate ends of the tube-like elements, said means being rotatable relative to the vehicle frame such that changes can be effected in the torsional stiiness of the torsion spring.

7. in a vehicle having a load-carrying frame and a pair of transversely-extending tandemly-disposed axles with load-supporting Wheels journaled on the ends of said axles, a pair of spring assemblies interconnecting the velncle frame and the axles such that said frame is resiliently supported on said axles, each of said spring assemblies comprising; a pair of tube-like torsion spring members, each of said spring members having a longitudinal axis and a generally cylindrical wall with an axially disposed slot extending the full length of said wallfor providing said spring member with ability to twist throughout its length in response to forces twistingly applied thereto, said twisting ability being characterized by relative movements between the slot-forming wall portions when said spring member is twisted; a force-reversing mechanism coupling the pair of tube-like spring members in force-transmitting axially-aligned end-to-end relationship so as to accommodate the twisting ability of each spring member, and such that a force twistingly applied tol one spring member in one direction is twistingly applied to the other spring member in an opposite direction; a pair of load-transmitting linkages connectingthe pair of tube-like spring members to respective portions of the pair of tandemly disposed axles, each of said linkages including an element circumferentially embracing a portion of the wall of one of said pair of spring members, and a spring-member-twisting connection between said element and embraced-wall portion, said embracement member, and so arranged with respect to the load-carrying frame that the one side of said frame is supported by the pair of spring members from the pair of axles through vthe pair of linkages, said supporting action being such that forces resulting therefrom are directly applied to the walls of the pair of spring members transversely of their axes and are converted to member-twisting forces twistingly applied to said pair of spring members by cooperative action of the force-reversing mechanism and said pair of load-transmitting linkages.

References Cited in the le of this patent UNITED STATES PATENTS 2,435,199 i Buckendne Feb. s, 194s 2,469,566 Low May 1o, 1949 FOREIGN PATENTS 872,258 France June 3, 1942 

